1. Field of the Invention
This invention relates in general to certain new and useful improvements in central locking devices used with passenger restraint systems, and more particularly, to an improved central locking device capable of receiving a plurality of belt lugs and which locking device precludes inadvertent release in a variety of settings including when the locking device is subjected to out-of-plane forces.
2. Brief Description of the Prior Art
The background of the invention with respect to central locking devices is exemplified in application Ser. No. 717,965 of this inventor filed Mar. 29, 1985, since abandoned and which is incorporated herein by reference. This referenced co-pending patent application discloses the general characteristics of central locking devices but is a fundamentally distinct structure from that of the present invention disclosed and claimed herein.
Belt locking devices used with passenger restraint systems are widely employed in aircraft, and particularly, military aircraft, where the belt locking device must releasably lock a plurality of hooks or so-called "lugs" on the ends of restraint belts. In military high performance aircraft, the locking device itself must receive the lugs on the ends of shoulder harness belts and a pair of waist harness belts as well as a crotch belt. These locking devices are often referred to as "multi-point" locking devices, as for example, a five point locking device which, as its name implies, receives five belt lugs.
One of the important criteria for these belt locking devices is that they must be capable of restraining the user with regard to his seat against any stresses caused by a sudden impact, as for example, in a crash. These locking devices should not be susceptible to user induced failure modes which would cause accidental premature release of the passenger. Moreover, these locking devices must also be capable of being readily and quickly opened so that all of the latches on the various belts can be quickly released from the locking device in order to permit a rapid exit from the aircraft or other vehicle. Another requirement is that the lugs must be installed without any activation of the operating lever.
There have been several different types of restraining system locking devices used in the field of high performance aircraft and helicopters. One of the central belt locking devices which has been commonly employed is that which comprises an upper locking disk or so-called "hub" hingedly mounted with respect to a spaced apart lower plate. The combination of the hub and plate defines a peripheral gap for releasably receiving the lugs on the ends of the restraining belts. In accordance with this construction, the upper disk or hub is actually rockably mounted in such a fashion that it can be shifted upwardly or downwardly at any point relative to the lower plate in order to receive or release a belt lug at any point of entry around the periphery thereof.
One of the central locking devices of the type previously described is illustrated and described in U.S. Pat. No. 4,403,376 to Palloks. In order to achieve the universal movement of the upper disk with respect to the lower locking plate so that the size of the gap which permits entry of the belt lug can vary, the device in the Palloks patent employs a conically shaped plug which supports the locking hub or so-called "cap-like housing". The plug extends through an aperture formed in the disk and is supported by the locking plate and in turn rockably supports the hub relative to the locking plate.
Belt locking devices of the type taught in the Palloks patent have been found to be highly effective when the forces imposed on the restraining belts and locked lugs are all "in plane", that is, when the tension or force placed on the restraining belts enforce the tension or pulling forces on the locked lugs and are in a plane which is parallel to the gap of the locking device. However, devices of the type taught in the Palloks patent are not effective when "out-of-plane" forces, that is, forces which are applied at an angle to the gap, are imposed on the belt locking system. In addition, the lugs cannot be inserted without activating the operating lever in a "DON" position.
In the typical passenger restraint system, particularly when shoulder harnesses, crotch harnesses and a waist harness are employed, the forces which may be imposed on the belts in a sudden impact as in a crash will typically be out-of-plane forces. The forces imposed on the shoulder harness will be clearly at an angle with respect to the forces on the waist harness and which will again be angled with respect to the forces imposed on the crotch harness. When this occurs in devices of the type taught in the Palloks patent, there tends to be an inadvertent separation of the belt lug from the locking device. Thus, such devices have been known to fail at their most critical point of need.
The plug in these prior art locking devices must be sufficiently soft to permit the disk to be deflected or tilted sufficiently to allow a locking lug to be introduced into the gap and snap fitted in the locking device. However, the softness of the plug also gives rise to the failures mentioned above. In locking devices exemplified by the Palloks patent, the plug is sufficiently soft so as to enable the rockable movement of the disk with respect to the lower rocking plate to vary the size of the gap. However, the softness of the metal of the plug permits out-of-plane forces to tilt the hub sufficiently to allow an inadvertent separation of the lugs from their locked position. Thus, the use of such a plug achieves a desirable low degree of frictional contact, but compromises the desired locking action against out-of-plane forces.
As a result of the foregoing, a need has arisen for a new and improved locking system. Specifically, five point belt locking devices must be capable of withstanding out-of-plane loads and must not inadvertently open under any circumstances. The present invention described and claimed herein eliminates this prior art deficiency and provides a device which is capable of withstanding out-of-plane loads without inadvertently opening and virtually eliminates failures. In addition the new design eliminates the requirement of setting the operating or actuation lever to a "DON" position to allow insertion of the lugs into the buckle.